Process for extracting minor fatty compounds which occur in a substance of biological origin

ABSTRACT

A method for extracting minor fatty compounds, partially steroids, from biological matter by means of cyclodextrin. According to the method, the cyclodextrin is stirred into said biological matter in a water-containing reaction medium to allow the formation of inclusion complexes between the cyclodextrin and the minor fatty compounds, whereafter said complexes are separated from said matter, the cyclodextrin being stirred in at a temperature such that the glycerides in said matter are in a congealed state.

TECHNICAL FIELD

The present invention relates to a process for extracting minor fatty compounds, especially steroids, and more particularly cholesterol, which occur in a substance of biological origin.

BACKGROUND OF THE INVENTION

"Minor fatty compounds" designates all non-glyceride fatty constituents which occur in natural fatty substances They may be steroids, especially sterols, fatty alcohols, fat-soluble vitamins, pigments, hydrocarbons, free fatty acids, abietic and pimaric acids, flavouring compounds and the like.

For more detail, reference can be made to the definition given in Manuel d'analyse des corps gras (Manual of the analysis of fatty acids)" JP WOLF--Ed Azoulay--Paris 1969, pages 11 and 25 .

Within the context of the present invention, the term "steroids" designates all compounds containing a more or less hydrogenated cyclopentanophenanthrene skeleton. Many of these compounds are alcohols and are termed sterols. They may occur in the form of esters especially of fatty acids, commonly designated by the term "cerides".

Cholesterol belongs to the sterol family. It has been known for some time that it is the main constituent of biliary calculi. Its reputation has recently been strengthened by its involvement in circulatory disorders, and more particularly the hardening of the arteries.

Nonesterified cholesterol is the main constituent of fatty substances of animal origin. These animal fats, which are present in most of our foodstuffs, constitute an important source of cholesterol which, in the event of an excess, may be the cause of serious cardiovascular diseases including myocardial infarction in particular.

Fatty substances of plant origin contain not cholesterol but phytosterols whose structure is very similar to it, such as for example: β-sitosterol, campesterol, stigmasterol, brassicasterol, Δ-7-stigmasterol, Δ-5-campesterol, Δ-5-avenasterol, Δ-7-avenasterol, Δ-7-9-sigmatadienol, fucosterol or ergosterol.

The process according to the invention also applies to the oxidised derivatives of steroids: sterones. These compounds occur especially in frying oils used repeatedly. Their presence in food products is not desirable as they are not devoid of toxic effect.

In addition, steroids are products of high added-value both economically and technically. Indeed, they have the potential of constituting high grade raw materials for the preparation of vitamin compounds (ergosterol: vitamin D2) or hormonal compounds (equilenin, oestrone, progesterone, testosterone or cortisone and the like). In addition to their pharmaceutical applications, steroids, and more particularly sterols and their fatty acid esters (cerides), may be used in the cosmetics industry as emulsifiers.

As far as the other minor fatty compounds are concerned, there may be distinguished, on the one hand, compounds which are undesirable from the food or technological point of view such as free fatty acids which promote oxidation, degradation compounds such as polymerised acids, foul-smelling compounds, colouring substances and savoury substances and the like; and on the other hand, compounds of high food or technological value such as fat-soluble vitamins, essential fatty acids (linoleic acid, α-linoleic acid, γ-linoleic acid, arachidonic acid, DHA and EPA), rare fatty acids (ricinoleic and abietic acids), and flavouring compounds.

There are thus several justifications for all the technological developments designed to extract the minor fatty compounds from fatty biological substances. This term designates in particular, on the one hand, animal fats, what they are storage fats such as fish oils or animal oils (tallow, chicken fat, lard and the like), structural fats such as those present in muscular, placenteral or nerve tissue (meat, egg, spinal cord, brain and the like) or fats from glandular secretion such as milk fats, or fats from skin secretion such as cerides (lanolin); and, on the other hand, vegetable fats. Finally, the fats may be a mixture of animal fats and vegetable fats such as margarines.

DESCRIPTION OF THE RELATED ART

Various methods for extracting minor fatty compounds from fat-containing biological substances have thus already been proposed.

Primarily, techniques exist for extracting steroids, especially cholesterol.

One of them consists in placing fatty substance of animal origin in contact with digitonin (digitogenin glucodise), which has the property of reacting with cholesterol to give an insoluble precipitate. The efficiency and the results of this method are not satisfactory due to the difficulty of separating the precipitate from the mixture. And in any case, this method is inapplicable industrially, especially for food products.

Cholesterol may also be extracted from fatty substances by entrainment by means of a solvent. The main disadvantage of this process is that the solvents generally used are toxic and that traces of them always remain in the fatty substances considered.

Processes of microdistillation, which are inapplicable at the industrial level, or alternatively of absorption on columns such as those described for example in European Patent Applications No. 0,174,848 and No. 0,318,326, are also known. These applications describe a process according to which the fatty substance, maintained in a liquid state, passes through an absorption column, in this case activated charcoal. It is evident that such a process is very hard to implement and, furthermore, the extraction which is achieved by it is not very selective.

Another physicochemical process for extracting cholesterol from fats is disclosed by Japanese Patent Application No. 59/140,299. It consists in placing a substance charged with cholesterol, such as milk powder, in contact with supercritical CO₂ at a temperature of between 35° and 45° C. and at a pressure of between 130 and 200 atm. Obtaining these physical conditions requires the use of complex and expensive equipment. Control of the process is thus very intricate as a result. Furthermore, as specified in the patent application, other lipid compounds are entrained by the supercritical CO₂. This process is not therefore selective.

A process for the biodegradation of the said sterols, which is described by European Patent Application No. 0,278,794, has also been conceived for removing sterols from fats. This process uses bacteria which, when placed in contact with the fatty substance, are capable of metabolising the sterols contained therein. Like all processes involving fermentations, this biodegradation process is very intricate to manage because of the inherent variability of living matter. Furthermore, the equipment used and the relatively long duration are, inter alia, elements which make such a process expensive. Finally, the catabolites produced during these fermentations remain up until now completely unknown with respect to their nature and their toxicity and are, in any case, present in the fatty substance thus treated.

A process for removing the cholesterol present in a fatty substance of animal origin is also disclosed by European Patent Application No. 0,256,911. It is based on the property, known since 1958, which is exhibited by cyclodextrins (cyclic polyglucose compounds of tubular frustoconical conformation containing 6, 7 or 8 glucose units and respectively designated by alpha-, beta- or gamma-cyclodextrin) whereby they accept sterol molecules, and especially cholesterol molecules, into their hydrophobic cavity to form inclusion complexes which are soluble in water. According to this process, the fatty substance, which is maintained fluid, is placed in contact, in an aqueous medium, with a cyclodextrin, with stirring and under a nonoxidising atmosphere for 30 minutes to 10 hours so as to allow the formation of complexes. Separation of the latter is then carried out by entrainment with water which solubilises these complexes. The aqueous solution thus obtained is then collected after decantation. The lipid phase obtained must be washed with water several times so as to remove the traces of complexes. The conditions for carrying out this process turn out to be relatively exacting. One of the main constraints to be met is the maintenance of a nitrogen-based nonoxidising atmosphere over the entire period during which the compounds are placed in contact. This period is moreover very long in practice since, if reference is made to the examples, it can be observed that it is always greater than or equal to 3 hours.

The yield of cholesterol extraction by this process is not very high. Indeed, in the best case, it is only 41%, and this after three successive extractions as indicated in Example 3 of the description of this European patent application.

The amount of water required for the placing in contact before separation corresponds to not less than 1000% by weight relative to the fatty substance to be treated.

Still on the same principle of using cyclodextrins for the extraction of steroids, European Patent Application No. 0,326,469 describes a process for removing steroidal compounds present in a substance of biological origin. According to this process, the substance of biological origin, which is made fluid if it is a solid fat at normal temperature, is placed in contact with a cyclodextrin in aqueous medium. The contacting is carried out with stirring for 5 hours at a temperature of the order of 40° C. A separation of the cyclodextrin/steroid complexes is then carried out. Here again, it should be noted that the actual duration of the placing in contact, which is given in all the examples, is very long: minimum of 5 hours.

The low yields of sterol extraction given in the examples are evidence that this process lacks efficiency.

During the placing in contact before separation, the reaction medium contains more than 100% by weight of water relative to the substance to be treated expressed on a dry basis.

Secondly, processes for extracting minor fatty compounds other than steroids have been considered.

Among these processes, the one described in U.S. Pat. No. 3,491,132 and designed to reduce the free fatty acid content of glyceridic oils using cyclodextrin may be mentioned. In this case, the cyclodextrin is placed in contact with the fatty medium in the presence of substantial amounts of water ranging from 200 to 1000% relative to the fatty medium treated.

These last three processes, which are described in European Patent Applications Nos. 0,256,911 and 0,326,469 and in U.S. Pat. No. 3,491,132, have at least one major disadvantage in common, namely that they take place in aqueous medium and require very large amounts of water for the placing in contact.

It is evident that the use of such amounts of water constitutes a handicap from the industrial point of view since it makes it necessary to handle large reaction volumes and requires equipment of large capacity which is therefore bulky and more expensive. Moreover, in addition to the high direct cost which this entails, the treatment of the effluents obtained after the separation should also be taken into account; this treatment representing a burden which increases as a function of the amount of effluent.

In view of the foregoing, it should be noted that the techniques for extracting minor fatty compounds using cyclodextrin, which are the most satisfactory nevertheless, especially with respect to the quality of the products obtained, have not been optimised from the point of view of economic and technical profitability.

SUMMARY OF THE INVENTION

Anxious to promote technical development in this field, the applicant company carried out long and numerous studies at the end of which they succeeded, to their credit, in finding that it was preferable and advantageous to carry out the placing in contact at a temperature at which the biological substance to be treated/cyclodextrin/water mixture is in a semisolid state, that is to say in a state where not all the substances present in the said substance are liquid.

Accordingly, the present invention relates to a process for extracting minor fatty compounds, especially steroids, and more particularly cholesterol, which occur in a substance of biological origin, using cyclodextrin, in which the cyclodextrin is placed in contact, with stirring and in a reaction medium containing water, with the substance to be treated so as to allow the formation of inclusion complexes between the cyclodextrin and the minor fatty compounds, these complexes being subsequently separated from the said substance, the process being characterised in that the placing in contact of cyclodextrin/substance to be treated is carried out at a temperature which is chosen such that the fatty substances present in the said substance are in a "congealed" state.

DETAILED DESCRIPTION OF THE INVENTION

Congealed state, within the context of the present invention, is understood to mean a state in which the level of solid or crystalline fatty substances is greater than or equal to 5% by weight.

This solid fat level is a common variable in the field of lipid technology. It is measured by low resolution Nuclear Magnetic Resonance, using pulsed minispectrometers.

Pulsed NMR, which is based on the fact that fat molecules in the liquid phase have a degree of mobility which is greater than that of the molecules of the solid phase, enables the percentage of solid or liquid fat to be determined. The principle and the applications of this method are described for example in the journal R.I.B.C. of January-February 1985 No. 80, pages 23 to 26, or in the journal I-A-A of May 1988, pages 463 to 471 or of June 1988, pages 463 to 470.

Contrary to what is recommended in the prior art and especially in European Patent Applications Nos. 0,256,911 and 0,326,469 and U.S. Pat. No. 3,491,132 which are mentioned above, the applicant company has demonstrated, surprisingly and unexpectedly, that the congealed state of the fatty substances which constitute the substance to be treated corresponds to an advantageous state for complexing minor fatty compounds, especially steroids, with cyclodextrin at the stage of placing in contact with stirring.

Preferably, the operating conditions are chosen such that the level of solid fats is greater than or equal to 10% and still more preferably greater than or equal to 30%.

In conformity with an advantageous arrangement of the present invention, the amount of water present in the reaction medium, during the placing in contact and before separation, is less than 100% by weight, preferably between 10 and 90%, and still more preferably between 20 and 60%, by weight relative to the substance to be treated expressed on a dry basis.

By thus limiting the amounts of water used, all the costs of implementing the extraction process are substantially reduced while making the use more flexible and easier.

Furthermore, the extraction yields are improved for much shorter durations of placing in contact, and the amounts of effluents collected, and therefore to be retreated, are substantially reduced. These effluents are in concentrated form, which keeps down the costs of transportation and retreatment.

The cyclodextrin used may be of the alpha, beta or gamma type, preferably of the beta type, which is substituted or unsubstituted. The mono- or poly-substituent groups of the cyclodextrin may be in particular alkyl groups such as the hydroxypropyl or ethyl group, or glycoside or maltosyl type saccharides and the like. Cyclodextrin rendered insoluble in water, for example by polymerisation, may also be chosen.

Advantageously, the cyclodextrin is used in the process according to the invention in pulverulent form. A cyclodextrin having a water content of less than or equal to 11% by weight, preferably less than or equal to 7% by weight, and still more preferably less than or equal to 5% by weight is preferably used. It may however be used after rehydration up to a water content of less than or equal to 15% by weight.

It is worthwhile to note that the placing in contact takes place under an ambient atmosphere. Indeed, the process conditions are not harsh and do not carry the risk of bringing about degradations, such as oxidation, of the sensitive fatty compounds (unsaturated fatty acids). Better still, cyclodextrin makes it possible, in addition, to remove, at least partially, the undesirable prooxidant compounds which may be present.

According to a preferred embodiment, the substance to be treated, water--if the said substance to be treated does not contain it or does not contain enough of it--and then cyclodextrin, preferably in pulverulent form, are placed together in a mixer equipped with kneading means. The sequence in which the products are introduced is preferably the one indicated above but it is also possible, among all the possible variants, for example to mix the substance to be treated and water beforehand.

Advantageously, the mixture is provided in a pasty form which is subjected, during the entire period of placing in contact, to a kneading operation during which the formation of cyclodextrin/minor fatty compound complexes occurs.

For the separation of these complexes, and this is also another novelty of the use of the process according to the invention, the kneaded paste is heated to a temperature which is chosen such that the fatty substances constituting the substance to be treated are in a molten state, that is to say in a state characterised by a level of solid or crystalline fatty substances which is less than 1% by weight.

This conversion to the molten state makes it possible to obtain, on the one hand, a phase containing the fatty substances and with a reduced content of minor fatty compounds and, on the other hand, a mixed water-lipid phase containing the cyclodextrin/minor fatty compound inclusion complexes.

These two phases separate from each other very well and it is therefore easy to collect the fatty phase free of the minor fatty compounds, which may then be used in various applications. The mixed phase, for its part, may be retreated to extract therefrom the minor fatty compounds which may be upgraded, especially in the pharmaceutical or cosmetics field.

When the substance to be treated is an animal and/or vegetable substance with a high lipid content such as for example butter which is concentrated or unconcentrated, tallow, lard, chicken fats, lanolins, hydrogenated vegetable oils, palm or copra fats, margarines and the like, it is introduced into a dough type kneading device provided with means for regulating the temperature.

Water is then optionally incorporated therein insofar as the substance of biological origin to be treated does mot contain it in a sufficient amount for the implementation of the process in conformity with the invention. The amount of water required is preferably between 20 and 60% by weight relative to the substance of biological origin to be treated, expressed on a dry basis.

Cyclodextrin is then added, preferably in pulverulent form and in sufficient amount to form inclusion complexes with the minor fatty compounds to be extracted.

The determination of the appropriate amount of cyclodextrin to be used is a function of the amount of minor fatty compounds to be extracted, and of their affinities for cyclodextrin. Generally, the amount of cyclodextrin is 0.5% to 15% relative to the substance of biological origin to be treated, expressed on a dry basis, preferably from 1 to 10% and more preferably from 3 to 8%.

The kneading of the paste formed by the mixing of these constituents is carried out at a temperature which is maintained constant by regulating means and chosen such that the fatty substance is in the congealed state with a level of solid or crystalline fats above 5%, preferably above 10% and more preferably between 30 and 50% by weight. For concentrated butter for example, the temperature is preferably chosen between about 10° and 25° C.

After a variable time, generally between 10 and 120 min, the kneading is stopped and the paste is heated sufficiently so that the level of solids in the fatty substance is less than 1% by weight. A water-lipid pellet containing the complexes and an oily liquid supernatant consisting of the fatty substance with a reduced minor fatty compound content are thereby formed.

As far as this embodiment for the process according to the invention is concerned, it should be noted that this process can be perfectly integrated within the framework of the manufacture of butter from cream. This manufacture essentially comprises the following stages:

biological or physical maturation (NIZO process) of the cream;

continuous or batch churning with emulsion reversal and separation of buttermilk;

optional kneading with biological maturation (NIZO process);

optional washing with water.

In conformity with the invention, cyclodextrin may be added after separation of the buttermilk, during the kneading. At the end of a placing in contact which is carried out at the churning temperature (less than 15° C.), the separation of the inclusion complexes formed is carried out by reverting to the molten state.

The process according to the invention enables steroids and in particular sterols to be extracted with yields as high as about 90% in a single treatment. These yields may be improved by increasing the number of treatments. These extraction efficiencies are obtained economically and easily in a relatively short time.

Another advantage of the process conforming to the invention is that it can permit the successive extraction of a certain number of minor fatty compounds from a substance of biological origin by controlling in a defined order one or more essential process parameters, namely in particular the mixing or kneading temperature, the amount of water present at the time of the complexing stage, the temperature for the change of phase, the pH of the medium.

The process according to the invention may be applied to natural fatty substances which are essentially composed of triglycerides but low in total phospholipids: that is to say having a total phospholipid content of less than 10% by weight relative to the total lipids.

This process permits, in particular, the extraction of steroids such as cholesterol from numerous biological substances. They may be animal fats and/or vegetable fats among which there may be mentioned:

milk fats such as concentrated or nonconcentrated butter;

animal fats such as tallow, lard, horse fat, chicken fats, fish oils, lanolin;

vegetable fats such as hydrogenated vegetable fats, palm oil, copra oil, cacao butter;

and mixtures thereof such as margarines.

In addition to removing these compounds from foodstuffs, the process conforming to the invention offers a useful source of steroids which are capable of being used in the preparation of pharmaceutical ingredients, especially hormonal and vitamin ingredients, or in the cosmetics industry as emulsifiers.

Naturally, the invention is not limited to the embodiments described above but, on the contrary, it encompasses all the variants thereof.

The following examples will make it possible to understand more clearly the process according to the present invention by demonstrating all the advantages offered by it.

EXAMPLE I Extraction of sterols, and more particularly cholesterol, which are present in a concentrated buffer in conformity with the process according to the invention

The concentrated butter used has a concentration of fatty substances of the order of 99.9%. The standard concentrated butter marketed by CORMAN (Belgium) is chosen for example.

The cyclodextrin is a beta-cyclodextrin of the type marketed by the applicant company under the registered trade mark KLEPTOSE and provided in the form of a white powder containing about 12% moisture.

1. Placing in contact

300 g of concentrated butter are introduced into the container of a dough mixer of the type marketed by KUSTNER. The container of the mixer is provided with a double wall in which a temperature-regulating fluid may be circulated. The mixer is started and the temperature is maintained at a mean value of about 14° C. At this temperature, the concentrated butter has a level of solid fats of about 28%.

150 g of water and 5.70 g of KLEPTOSE cyclodextrin are then added successively. The placing in contact then proceeds for 30 minutes.

2. Separation of the inclusion complexes

The pasty concentrated butter/water/cyclodextrin mixture removed from the mixer is heated to a temperature of the order of 37° C. (level of solid fats of the concentrated butter less than 1%). A change of phase occurs spontaneously and a pasty pellet is obtained containing in particular the inclusion complexes and water. This pellet is covered by an oily phase formed by the decholesterolised concentrated butter. More than 94% by weight of the concentrated butter used can then be recovered.

The cholesterol is assayed by a colorimetric method after oxidation to cholestenone using cholesterol oxidase, according to the method of, and using the reagents with the reference no. 139 050 from, BOEHRINGER Mannheim.

The initial cholesterol content of the concentrated butter is 0.270% by weight.

The final content is 0.038%.

The extraction yield therefore amounts to 86%.

A second extraction, carried out under the same conditions, provides a yield of 74%, which gives an overall yield of 96%.

It can be observed that the efficiency of the process according to the invention is quite remarkable both from the point of view of the amount and that of the duration.

The amount of water used is quite small and poses no problem of handling.

The pasty pellet containing water which is used represents only 173 g. This small and concentrated amount poses no problem with respect to its retreatment.

EXAMPLE II Extractions of sterols, and more particularly cholesterol, which are present in butter in conformity with the invention

In this example, 9 tests for extracting cholesterols from concentrated butter were carried out using the same equipment and by following the same procedure as in Example I. Certain experimental parameters were simply changed. The data and results of these tests are presented in Table I below:

                  TABLE I                                                          ______________________________________                                          Tests                                                                               ##STR1##  in °C.temperatureMean                                                             ##STR2##                                                                                minutescontact inplacing inDuration                                                    in 90yield                          ______________________________________                                         1    20      60    15      5    15    30      65                               2    30      90    15      5    15    30      85                               3    50     150    15      5    15    30      84                               4    100    300    15      5    15    30      75                               5    50     150    16      7    21    30      93                               6    50     150    16      5    15    15      75                               7    50     150    26.5    5    15    30      65                               8    50     150    16      3     9    30      59                               9    50     150    16      3     9    120     55                               ______________________________________                                          *CD = cyclodextrin                                                             (1) % relative to concentrated butter                                          (2) % relative to concentrated butter                                    

Comments on Table I

By comparing the results of tests 1 to 4 which differ only in the amount of water used, it can be observed that the cholesterol extraction yield, expressed in %, is maximum for water contents of between 30 and 50% relative to concentrated butter. The increase in the water content brings about a drop in the extraction yield.

By comparing the results of tests 3 and 5 for which only the KLEPTOSE cyclodextrin concentration is different (5 and 7% respectively relative to concentrated butter), it can be observed that it is possible to increase the extraction yield by 9% purely by increasing the cyclodextrin concentration by 2%.

In test 6, the duration of kneading was reduced to 15 minutes. The yield obtained is 75%, which constitutes a very satisfactory result.

For test 7, the temperature of placing in contact was increased to 26.6° C. By reducing the solids level in the concentrated butter, the cholesterol extraction yield is reduced (65% against 84% for test 3).

By using 3% cyclodextrin relative to concentrated butter (tests 8 and 9), it can be observed that beyond 30 min, prolonging the kneading does not enable the yields to be increased.

EXAMPLE III Extraction of sterols, and more particularly cholesterol, which are present in butter in conformity with the present according to the invention

The butter used in this example is a commercial butter containing 82% of fatty substances.

The cyclodextrin, the equipment as well as the procedure are the same as for the preceding examples, the only difference being that no water is added: it is the butter itself which provides the water required for complex formation.

The data and results of this example are given in Table II below:

                                      TABLE II                                     __________________________________________________________________________     Water                CD* KLEPTOSE                                              % relative   Mean    % relative  Duration o f placing                                                                     Extraction                          to FS*    g  temperature °C.                                                                 to FS*    g in contact                                                                               yield in %                          __________________________________________________________________________     Butter                                                                             20.5  25.5                                                                              12      5         7.5                                                                              45        80                                  150 g                                                                          __________________________________________________________________________      *FS = Fatty Substance                                                    

It is shown here that the process according to the invention is also effective on a substance to be treated initially containing water in an amount conforming to the characteristics of the present invention.

EXAMPLE IV Extraction of sterols, and more particularly cholesterol, which are present in tallow, in conformity with the process according to the invention

200 g of tallow containing 99% of fatty substances, of the type marketed by ROUSSELOT, are treated in the same manner as in the preceding examples.

The initial cholesterol content of the tallow is 0.12% by weight.

Table III below shows the data and the results of the present example.

                                      TABLE III                                    __________________________________________________________________________     Water                CD* KLEPTOSE                                              % relative   Mean    % relative  Duration o f placing                                                                     Extraction                          to FS*    g  temperature °C.                                                                 to FS*    g in contact                                                                               yield in %                          __________________________________________________________________________     Tallow                                                                             50    100                                                                               16      3         6 30        83                                  200 g                            60        82                                      25     50                                                                               16      3         6 30        86                                                                   60                                            __________________________________________________________________________

Comments on Table III

It appears that an amount of water of 25% by weight relative to the tallow is sufficient to extract 86% of the initial cholesterol, and this with only 3% by weight of cyclodextrin relative to the tallow.

An increase in the amount of water and/or the duration of placing in contact does not enable the extraction yield to be improved.

In this example, the variations in the acid values were also measured. The acid value is defined as the number of mg of potassium hydroxide required to neutralise the acidity of 1 g of tallow. The acid value of tallow before extraction is 0.85.

Table IV below presents the results obtained.

                                      TABLE IV                                     __________________________________________________________________________     Water,           CD Kleptose,                                                                          Duration                                                                             Final                                                                              %                                            % relative                                                                               Temperature                                                                           % relative                                                                            of placing                                                                           acid                                                                               reduction in                                 to tallow °C.                                                                            to tallow                                                                             in contact                                                                           value                                                                              the value                                    __________________________________________________________________________     Tallow                                                                             50    26     3      30    0.65                                                                               30                                           200 g                                                                              25    16     3      30    0.12                                                                               86                                           __________________________________________________________________________

It is shown here that the decrease in acid value, and therefore of the free fatty acid content, of the tallow is very pronounced with 25% of water. 

We claim:
 1. In a process for extracting minor fatty compounds from a substance of biological origin containing fatty substances, comprising the steps of:selecting a substance of biological origin containing fatty substances and minor fatty compounds, selecting a cyclodextrin capable of forming inclusion complexes with the said minor fatty compounds, contacting the cyclodextrin with the substance of biological origin in a reaction medium comprising water for a time sufficient to form said inclusion complexes, separating the said inclusion complexes formed during the contacting step from the said substance of biological origin, the improvement which comprises selecting as a temperature during the contacting step the temperature at which at least 5% by weight of the fatty substances present in said substance of biological origin are in a solid or crystalline state.
 2. A process according to claim 1, wherein the temperature during the contacting step is the temperature at which at least 10% by weight of the fatty substances present in the substance of biological origin are in a solid or crystalline state.
 3. A process according to claim 1, wherein the temperature during the contacting step is the temperature at which at least 30% by weight of the fatty substances present in the substance of biological origin are in a solid or crystalline state.
 4. A process according to claim 1, wherein the amount of water in the reaction medium is less than 100% by weight relative to the dry matter of the substance of biological origin.
 5. A process according to claim 1, wherein the amount of water in the reaction medium is of between 10 and 90% relative to the dry matter of the substance of biological origin.
 6. A process according to claim 1, wherein the amount of water in the reaction medium is of between 20 and 60% relative to the dry matter of the substance of biological origin.
 7. A process according to claim 1, wherein the cyclodextrin is; a β-cyclodextrin which is substituted or unsubstituted.
 8. A process according to claim 1, wherein the minor fatty compounds are steroids, fatty alcohols, free fatty acids, fat-soluble vitamins, pigments, hydrocarbons, abietic and pimaric acids, flavouring compounds.
 9. A process according to claim 1, wherein the substance of biological origin is concentrated butter.
 10. A process according to claim 9, wherein the contacting temperature is between about 10° and 25° C.
 11. A process according to claim 1, wherein the substance of biological origin is dairy cream.
 12. A process according to claim 11, wherein the contacting temperature is less than 15° C.
 13. A process according to claim 1, wherein the cyclodextrin is used in pulverulent form and has a water content less than or equal to 11% by weight.
 14. A process according to claim 1, wherein the amount of cyclodextrin is of 0.5% to 15% by weight relative to the dry matter of the substance of biological origin.
 15. A process according to claim 1, wherein the amount of cyclodextrin is of 1 to 10% by weight relative to the dry matter of the substance of biological origin.
 16. A process according to claim 1, wherein the amount of cyclodextrin is of 3 to 8% by weight relative to the dry matter of the substance of biological origin.
 17. A process according to claim 1 wherein the separation of the inclusion complexes between the cyclodextrin and the minor fatty compounds is carried out by heating the reaction medium to a temperature at which at most 1% of the fatty substances present in the substance of biological origin are in a solid or crystalline state and by separating, on the one hand, the phase containing the fatty substances with a reduced content of minor fatty compounds and, on the other hand, the mixed water-lipid phase containing the inclusion complexes between the cyclodextrin and the minor fatty compounds. 